1. Field of the Invention
The present invention relates to sub-surface, equipment housing devices, and particularly to prefabricated pits designed for use in servicing aircraft at docking, loading and refueling terminals.
2. Description of the Prior Art
Servicing of aircraft on the ground at modern airport terminals is frequently performed using prefabricated pits which are installed at aircraft docking, fueling and loading areas. The pre-fabricated pits are installed beneath the surface of the tarmac across which aircraft travel during docking, refueling and departure maneuvers. The pits are typically formed of fiberglass, steel or aluminum, and are constructed as enclosures with surrounding walls, a floor, and an access cover at the top of the walls. The pits are installed below the surfaces of loading and refueling aprons at aircraft terminals, remote parking locations and maintenance bases.
Pre-fabricated pits of this type are used to allow ground support functions to be carried out from sub-surface enclosures. These ground support functions include the provision of fuel, the provision of electricity to aircraft located in the docking area, the provision of air for cooling the aircraft interior and pressurizing air for starting engines of the aircraft,and for other aircraft support activities which are conducted on the ground. The use of sub-surface pits eliminates the need for mobile trucks, carts and other vehicles which are otherwise present in the loading area and which interfere with the arrival and departure of aircraft in the vicinity of the loading gate. The use of sub-surface pits allows the provision of fuel, power, cooling and pressurized air, and other supplies from a central location. The necessary fluid supplies and electrical power can be generated or stored with great efficiency at a central location, as contrasted with the conduct of such ground support functions from mobile generating or supply vehicles.
The sub-surface, pre-fabricated pits used for ground support functions typically house valves, electrical plugs, junction boxes, cooling air terminations and other terminal equipment used to service aircraft that have been docked. Umbilical pipes and lines, and electrical conduits otherwise stored within the pits, are withdrawn from the pits through hatches therein and are coupled to the docked aircraft to supply the aircraft with fuel, air for cooling the aircraft interiors, pressurized air for starting the engines and electrical power.
One problem in connection with conventional sub-surface pit assemblies is the possibility of exposure of instruments, equipment and especially electrical power outlets and electrically operated devices to water due to flooding. Sub-surface pits are normally exposed to a variety of weather conditions. Despite pit designs which attempt to make such servicing pits waterproof, quite frequently leaks in the pits will develop, especially after the pits have been in service for several years.
Pits are designed and constructed so as to be able to withstand pressure from normal water table conditions so that the pits do not flood and so that the equipment within the pits does not become submerged. However, even with high quality, waterproof pit designs, a sub-surface aircraft servicing pit, will, upon some occasions, be subjected to such extreme flooding conditions that even the best pits commercially available are not flood-proof. When servicing pits flood significant problems develop within water sensitive equipment and articles, and electrical equipment and outlets in particular. Short circuits develop within the system, and the equipment in the pit is rendered useless, at least temporarily, and the equipment frequently is severly damaged. Moreover, with electrical short circuits a very dangerous condition exists since attempted use of the pits can result in severe electrical shock, and even death.